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Digital in-line holography is a versatile method to obtain lens-less images of small particles, such as aerosol particles, ranging from several to over one hundred microns in size. It has been shown theoretically, and verified by measurement, that a particle’s extinction cross section can also be obtained from a digital hologram. The process involves a straightforward integration, but if noise is present it fails to give accurate results. Here we present a method to reduce the noise in measured holograms of single particles for the purpose of rendering the cross-section estimation more effective. The method involves masking the complex-valued particle image-amplitude obtained from a noisy hologram followed by a Fresnel transformation to generate a new noise-reduced hologram. Examples are given at two wavelengths, 440 nm and 1040 nm, where the cross section is obtained for a micro-sphere particle and several non-spherical particles approximately 50 microns in size.
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Isolating single-particle holograms in a multiparticle digital hologram
A method is developed to isolate the interference-fringe pattern associated with an individual particle from a single digital in-line hologram containing overlapping patterns from multiple particles. The method is illustrated with a measured hologram of road-dust aerosol particles nominally 20-50 µm in size. It is further tested for 2.5-3.0 µm particles by simulation with the discrete dipole approximation. By incrementally degrading a hologram’s resolution, the method is shown to perform well for particles that are poorly resolved, at least for the first few central fringes in the pattern. The method may be useful in cases where particle characterization is done directly from a hologram, i.e., instead of from the reconstructed images.
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- Award ID(s):
- 2107715
- PAR ID:
- 10577474
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Continuum
- Volume:
- 4
- Issue:
- 3
- ISSN:
- 2770-0208
- Format(s):
- Medium: X Size: Article No. 668
- Size(s):
- Article No. 668
- Sponsoring Org:
- National Science Foundation
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